In Japanese Laid Patent No. 2001-319502, a light source apparatus which uses a xenon lamp as a light source of a projector is disclosed. As in Japanese Laid Patent No. 2001-319502, FIG. 6 shows a cross sectional view of a lamp of a conventional light source apparatus 100, taken along a longitudinal direction thereof, in which a short arc type xenon lamp is used. In the figure, xenon gas whose pressure becomes 2-8 MPa at time of lighting, is enclosed in a spherical bulb 111 of a short arc type xenon lamp 101, and a pair of electrodes 112 is arranged inside thereof. A pair of sealing portions 113 which hold the respective electrodes 112 is provided in both ends of the bulb 111, and mouthpieces 114 and 115 are provided in the respective sealing portions 113. The pair of electrodes 112 is connected with a power supply (not shown), and the xenon lamp 101 is turned on when rated lighting electric power of 2-7 kW is inputted therein. At time of lighting of the xenon lamp 101, since a distance between the electrodes 112 which face each other is short (close to each other), a diameter of an arc becomes short so as to become a small point light source.
One (114) of the pair of mouthpieces 114 and 115 which are arranged at the both ends of the xenon lamp 101 is held by a first lamp holding section 102, and on the other hand, the mouthpiece 115 is held by a second lamp holding section 103. Reflection mirrors 104 and 105 are arranged so that the bulb 111 of the xenon lamp 101 may be surrounded by and provided between the mouthpieces 114 and 115. The reflection mirrors 104 and 105 are provided so that focal points thereof and a focal point (point light source) of the xenon lamp 101 may be matched each other. The first lamp holding section 102, the second lamp holding section 103, and reflection mirrors 104 and 105 are supported on a support plate 106. The support plate 106 is installed in a projector (not shown).